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Test Particles Dynamics In 3d Non Linear Magnetohydrodynamics Simulations And Application To Runaway Electron Formation In Tokamak Disruptions
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Book Synopsis Test Particles Dynamics in 3D Non-linear Magnetohydrodynamics Simulations and Application to Runaway Electron Formation in Tokamak Disruptions by : Cristian Sommariva
Download or read book Test Particles Dynamics in 3D Non-linear Magnetohydrodynamics Simulations and Application to Runaway Electron Formation in Tokamak Disruptions written by Cristian Sommariva and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In view of better understanding Runaway Electron (RE) generation processes during tokamak disruptions, this work investigates test electron dynamics during a JET disruption simulated with the JOREK code. For this purpose, a JOREK module computing relativistic test particle orbits in the simulated fields has been developed and tested. The study shows that a significant fraction of pre-disruption thermal electrons remain confined in spite of the magnetic chaos characterizing the Thermal Quench (TQ) phase. This finding, which is related to the prompt reformation of closed flux surfaces after the TQ, supports the possibility of the so-called “hot tail” RE generation mechanism. In addition, it is found that electrons may be significantly accelerated during the TQ due to the presence of strong local electric field (E) fluctuations related to magnetohydrodynamic (MHD) activity. This phenomenon, which has virtually been ignored so far, may play an important role in RE generation. In connection to this modelling work, an experimental study on ASDEX Upgrade disruptions has been performed, suggesting that strong MHD activity reduces RE production.
Book Synopsis Improved Macroscopic Plasma Modeling and Its Application to Tokamak Disruptions by : Brian Cornille
Download or read book Improved Macroscopic Plasma Modeling and Its Application to Tokamak Disruptions written by Brian Cornille and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents results from two topics in tokamak disruption modeling. The first usessimulation to elucidate the observations from MST tokamak disharge experiments on suppression of runaway electrons (RE) with resonant magnetic perturbations (RMP). When applying RMPs having a single poloidal harmonic, an m = 1 RMP does not suppress RE while and m = 3 RMP achieves full suppression [Munaretto et al., Nuclear Fusion 60, 046024 (2020)]. Magnetohydrody- namics (MHD) simulation of the experiment indicates that the m = 3 RMP produces a substantial region of chaotic magnetic fields whereas the m = 1 RMP produces negligible changes in field topology compared to no RMP. Using snapshots of the MHD simulation fields, full-orbit relativis- tic electron test particle computations show [approximately equal to] 50% loss from the m = 3 RMP compared to the 10 -15% loss from the m = 1 RMP. Test particle computations of the m = 3 RMP case in the time-evolving MHD simulation fields show correlation between MHD activity and enhanced particle losses, but finds similar total electron confinement and field snapshots. The second topic presents a novel enhancement to vertical displacement computations in NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. We present development of a quasi-static meshed vacuum region approach for treatment of computations with a resistive wall representation. With this approach a magnetostatic problem is solved for an external vacuum region while coupled through a thin-wall approximation to the implicit time advance of the plasma. Verification of the implementation is presented along with demonstration of its increased robustness in challenging geometries compared to the incumbent implementation.
Book Synopsis Magnetohydrodynamic Stability of Tokamaks by : Hartmut Zohm
Download or read book Magnetohydrodynamic Stability of Tokamaks written by Hartmut Zohm and published by John Wiley & Sons. This book was released on 2015-02-09 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book bridges the gap between general plasma physics lectures and the real world problems in MHD stability. In order to support the understanding of concepts and their implication, it refers to real world problems such as toroidal mode coupling or nonlinear evolution in a conceptual and phenomenological approach. Detailed mathematical treatment will involve classical linear stability analysis and an outline of more recent concepts such as the ballooning formalism. The book is based on lectures that the author has given to Master and PhD students in Fusion Plasma Physics. Due its strong link to experimental results in MHD instabilities, the book is also of use to senior researchers in the field, i.e. experimental physicists and engineers in fusion reactor science. The volume is organized in three parts. It starts with an introduction to the MHD equations, a section on toroidal equilibrium (tokamak and stellarator), and on linear stability analysis. Starting from there, the ideal MHD stability of the tokamak configuration will be treated in the second part which is subdivided into current driven and pressure driven MHD. This includes many examples with reference to experimental results for important MHD instabilities such as kinks and their transformation to RWMs, infernal modes, peeling modes, ballooning modes and their relation to ELMs. Finally the coverage is completed by a chapter on resistive stability explaining reconnection and island formation. Again, examples from recent tokamak MHD such as sawteeth, CTMs, NTMs and their relation to disruptions are extensively discussed.
Download or read book Fusion Energy Update written by and published by . This book was released on 1982 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 3D Nonlinear Magnetohydrodynamic Simulations of Macroscopic Internal Instabilities in Tokamak Plasmas by : Isabel Krebs
Download or read book 3D Nonlinear Magnetohydrodynamic Simulations of Macroscopic Internal Instabilities in Tokamak Plasmas written by Isabel Krebs and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 3D Simulation Studies of Tokamak Plasmas Using MHD and Extended-MHD Models by :
Download or read book 3D Simulation Studies of Tokamak Plasmas Using MHD and Extended-MHD Models written by and published by . This book was released on 1997 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The M3D (Multi-level 3D) tokamak simulation project aims at the simulation of tokamak plasmas using a multi-level tokamak code package. Several current applications using MHD and Extended-MHD models are presented; high-[beta] disruption studies in reversed shear plasmas using the MHD level MH3D code, [omega]{sub *i} stabilization and nonlinear island rotation studies using the two-fluid level MH3D-T code, studies of nonlinear saturation of TAE modes using the hybrid particle/MHD level MH3D-K code, and unstructured mesh MH3D{sup ++} code studies. In particular, three internal mode disruption mechanisms are identified from simulation results which agree well with experimental data.
Book Synopsis Simulation of Tokamak Runaway-electron Events by :
Download or read book Simulation of Tokamak Runaway-electron Events written by and published by . This book was released on 1987 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Two-Fluid and Resistive Nonlinear Simulations of Tokamak Equilibrium, Stability, and Reconnection by :
Download or read book Two-Fluid and Resistive Nonlinear Simulations of Tokamak Equilibrium, Stability, and Reconnection written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The NIMROD and M3D / M3D-C1 codes now each have both a resistive MHD and a two-fluid (2F) capability including gyroviscosity and Hall terms. We describe: (1) a nonlinear 3D verification test in the resistive MHD regime in which the two codes are in detailed agreement, (2) new studies that illuminate the effect of two-fluid physics on spontaneous rotation in tokamaks, (3) studies of nonlinear reconnection in regimes of relevance to fusion plasmas with peak nonlinear reconnection rates that are essentially independent of the resistivity, and (4) linear two-fluid tearing mode calculations including electron mass that agree with analytic studies over a wide range of parameter regimes.
Book Synopsis Test Particle Studies of Acceleration and Transport in Solar and Tokamak Plasmas by : Robert McKay
Download or read book Test Particle Studies of Acceleration and Transport in Solar and Tokamak Plasmas written by Robert McKay and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A test particle approach is used to study two distinct plasma physics situations. In the first case, the collisionless response of protons to cold plasma fast Alfven waves propagating in a non-uniform magnetic field configuration (specifically, a two-dimensional X-point field) is studied. The field perturbations associated with the waves, which are assumed to be azimuthally-symmetric and invariant in the direction orthogonal to the X-point plane, are exact solutions of the linearized ideal magnetohydrodynamic (MHD) equations. The protons are initially Maxwellian, at temperatures that are consistent with the cold plasma approximation. Two kinds of wave solution are invoked: global perturbations, with inward- and outward-propagating components; and purely inward-propagating waves, localised in distance from the X-point null, the wave electric field E having a preferred direction. In both cases the protons are effectively heated in the direction parallel to the magnetic field, although the parallel velocity distribution is generally non-Maxwellian and some protons are accelerated to highly suprathermal energies. This heating and acceleration can be attributed to the fact that protons undergoing E x B drifts due to the presence of the wave are subject to an effective force in the direction parallel to B. The localised wave solution produces more effective proton heating than the global solution, and successive wave pulses have a synergistic effect. This process, which could play a role in both solar coronal heating and late-phase heating in solar flares, is effective for all ion species, but has a negligible direct effect on electrons. However, both electrons and heavy ions would be expected to acquire a temperature similar to that of the protons on collisional timescales. In the second case the same approach is used to study the collisional transport of impurity ions (carbon, mainly, although tungsten ions are also simulated) in spherical tokamak (ST) plasmas with transonic and subsonic toroidal flows. The efficacy of this approach is demonstrated by reproduscing the results of classical transport theory in the large aspect ratio limit. The equilibrium parameters used in the ST modelling are similar to those of plasmas in the MAST experiment. The effects on impurity ion confinement of both counter-current and co-current rotation are determined. Various majority ion density and temperature profiles, approximating measured profiles in rotating and non-rotating MAST plasmas, are used in the modelling. It is shown that transonic rotation (both counter-current and co-current) has the effect of reducing substantially the confinement time of the impurity ions. This effect arises primarily because the impurity ions, displaced by the centrifugal force to the low-field region of the tokamak, are subject to a collisional diffusivity that is greater than the flux surface-averaged value of this quantity. for a given set of plasma profiles, the carbon ions are found to be significantly less well-confined in co-rotating plasmas than in counter-rotating plasmas, although the difference in confinement time between co- and counter-rotation lessens as the mass of the impurity increases. In the case of carbon ions the poloidal distribution of losses exhibits a pronounced up/down asymmetry that is consistent with the direction of the net vertical drift of the impurity ions. Increasing the mass of the impurity ion is also found to significantly decrease the confinement time in the rotating cases, though the confinement time for the case of a stationary plasma is increased. Such studies of impurity transport within tokamaks are important because it is desirable to expel impurity ions from the plasma to avoid both dilution of the fuel ions and unacceptable radiation losses from the plasma.
Book Synopsis Nonlinear Magnetohydrodynamics by : D. Biskamp
Download or read book Nonlinear Magnetohydrodynamics written by D. Biskamp and published by Cambridge University Press. This book was released on 1997-07-17 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: A self-contained introduction to magnetohydrodynamics with emphasis on nonlinear processes.
Book Synopsis Simulation of Tokamak Runaway-electron Events. Study Oftheresponse of Materials by Use of an Electron Linear Accelerator by : H. Bolt
Download or read book Simulation of Tokamak Runaway-electron Events. Study Oftheresponse of Materials by Use of an Electron Linear Accelerator written by H. Bolt and published by . This book was released on 1987 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Phase-space Dynamics of Runaway Electrons In Tokamaks by :
Download or read book Phase-space Dynamics of Runaway Electrons In Tokamaks written by and published by . This book was released on 2010 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: The phase-space dynamics of runaway electrons is studied, including the influence of loop voltage, radiation damping, and collisions. A theoretical model and a numerical algorithm for the runaway dynamics in phase space are developed. Instead of standard integrators, such as the Runge-Kutta method, a variational symplectic integrator is applied to simulate the long-term dynamics of a runaway electron. The variational symplectic integrator is able to globally bound the numerical error for arbitrary number of time-steps, and thus accurately track the runaway trajectory in phase space. Simulation results show that the circulating orbits of runaway electrons drift outward toward the wall, which is consistent with experimental observations. The physics of the outward drift is analyzed. It is found that the outward drift is caused by the imbalance between the increase of mechanical angular momentum and the input of toroidal angular momentum due to the parallel acceleration. An analytical expression of the outward drift velocity is derived. The knowledge of trajectory of runaway electrons in configuration space sheds light on how the electrons hit the first wall, and thus provides clues for possible remedies.
Book Synopsis SIMULATION OF TOKAMAK RUNAWAY-ELECTRON EVENTS - STUDY OF THE RESPONSE OFMATERIALS BY USE OF AN ELECTRON LINEAR ACCELERATOR. by : H. Bolt
Download or read book SIMULATION OF TOKAMAK RUNAWAY-ELECTRON EVENTS - STUDY OF THE RESPONSE OFMATERIALS BY USE OF AN ELECTRON LINEAR ACCELERATOR. written by H. Bolt and published by . This book was released on 1987 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Euro Abstracts written by and published by . This book was released on 1989 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Center for Gyrokinetic/MHD Hybrid Simulation of Energetic Particle Physics in Toroidal Plasmas (CSEPP). Final Report by :
Download or read book Center for Gyrokinetic/MHD Hybrid Simulation of Energetic Particle Physics in Toroidal Plasmas (CSEPP). Final Report written by and published by . This book was released on 2012 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Colorado University-Boulder the primary task is to extend our gyrokinetic Particle-in-Cell simulation of tokamak micro-turbulence and transport to the area of energetic particle physics. We have implemented a gyrokinetic ion/massless fluid electron hybrid model in the global [delta] f-PIC code GEM, and benchmarked the code with analytic results on the thermal ion radiative damping rate of Toroidal Alfven Eigenmodes (TAE) and with mode frequency and spatial structure from eigenmode analysis. We also performed nonlinear simulations of both a single-n mode (n is the toroidal mode number) and multiple-n modes, and in the case of single-n, benchmarked the code on the saturation amplitude vs. particle collision rate with analytical theory. Most simulations use the f method for both ions species, but we have explored the full-f method for energetic particles in cases where the burst amplitude of the excited instabilities is large as to cause significant re-distribution or loss of the energetic particles. We used the hybrid model to study the stability of high-n TAEs in ITER. Our simulations show that the most unstable modes in ITER lie in the rage of 10
Book Synopsis Nonlinear MHD Simulations of Spherical Tokamak and Helical Plasmas by : T. Hayashi
Download or read book Nonlinear MHD Simulations of Spherical Tokamak and Helical Plasmas written by T. Hayashi and published by . This book was released on 2002 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 3D Simulation Studies of Tokamak Plasmas Using MHD and Extended-MHD Models by : Wonchull Park
Download or read book 3D Simulation Studies of Tokamak Plasmas Using MHD and Extended-MHD Models written by Wonchull Park and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
